1. Field of the Invention
The present invention relates to a sheet-shaped light guide, and particularly, to a sheet-shaped light guide which includes light-scattering particles in a sheet-shaped optical medium and propagates light incident from one end face of the light guide to the other end face side thereof while scattering the light by means of the particles.
Moreover, the present invention relates to a communication system using the sheet-shaped light guide.
2. Description of the Related Art
Heretofore, as described in, for example, U.S. Pat. Nos. 5,548,670 and 5,542,017, a light guide which includes particles for scattering light in an optical medium, such as PMMA (poly-methyl methacrylate), and which propagates light incident from one end face thereof to the other end face side thereof while scattering the light by means of the particles, is known.
Such a light guide propagates light by using the effect of total reflection at the interface between the side face of the light guide and a surrounding medium (air or cladding layer) while repeatedly scattering the light by means of the particles in the optical medium. Accordingly, when compared to a light guide which propagates light only by using the effect of total reflection, such a light guide has an advantage that it is possible to allow light, the intensity distribution of which is made even, to be emitted from an exit end face. As for this kind of a light guide, as described in, for example, U.S. Pat. No. 5,822,475, by utilizing such an advantage, it is conceived to apply the light guide in order to constitute an optical data bus (sheet bus). The optical data bus is formed by use of a sheet-shaped optical medium. One input part for inputting optical signals is coupled to one end face of the sheet-shaped optical medium, and a plurality of output parts are coupled to the other end face thereof. Therefore, the optical data bus distributes an inputted optical signal as a common signal to the plurality of output parts.
Moreover, as an optical data bus of this type, as described in, for example, Japanese Unexamined Patent Publication No. 11(1999)-031035, one, in which light diffusion portions are provided on a light-incident-side end portion of the sheet-shaped optical medium so as to correspond to respective signal light incident portions, and the signal light, which is diffused and branched by the light diffusion portions, is propagated toward a light-emitting-side end portion of the optical medium, is also known.